The invention relates to a lift and pivot device for a cover of a furnace, and also a furnace system equipped therewith, in particular an electric arc furnace system. The invention furthermore relates to a method for use with such a furnace system.
In order to charge a furnace, in particular an electric arc furnace, where primarily scrap metal is charged as the charge material, a furnace vessel of the electric arc furnace normally closed during the melting process is opened. To this end, electrode carrying arms which are present with electrodes attached thereto and also the cover of the furnace are lifted and pivoted to the side with a rotational movement. Normally this is done by rotating these assemblies around a common pivot point. The charge material is then introduced into the furnace vessel, the assemblies are pivoted back into the original position and lowered again such that the furnace vessel is closed again and the next melting process can be started.
Lift and pivot devices of the type mentioned in the introduction are already known inter alia from DE 35 14 293 A1. Here it is described that the device comprises a liftable and pivotable support member which engages on the edge of the cover. A lift device is fastened on a laterally pivotable frame arranged beside the furnace vessel. In the lowered position the support member is released from the edge of the cover. On being raised it engages with a lift eye, matched to the form of the support member, on the edge of the cover.
EP 0 077 319 A1 describes an electric furnace having a lifting mechanism operating a furnace cover. The lifting mechanism has a fixed support pin and a lifting device arranged inside the support pin, which actuates a lifting column which is to engage with and disengage from the furnace cover. The lifting column is guided in axially movable fashion on the support pin by an upper and a lower bearing. The lifting device, in particular in the form of a hydraulic cylinder, is connected at one end in articulated fashion to the lifting column and at the other end in articulated fashion to a fixed part of the system, such as a base or the support pin.
Large masses are normally moved by such a lift and pivot device, during which process high axial and vertical forces are generated on the rotation and guide bearings of the lift and pivot device. This results in high material stress levels and renders necessary recurring servicing work and strict controls. To ensure correct lifting and lowering of the cover, the guide bearings must therefore not exceed certain tolerances in order to avoid jamming or wedging of the guide facilities and/or of the lift cylinders used.